1. Field of the Invention
The invention relates to fluid level sensing assemblies. More particularly, the invention relates to fluid level sensing assemblies capable of accurately determining the level of a fluid within a reservoir by analyzing output signals of the fluid level sensing assembly.
2. Description of the Related Art
The storage and delivery of liquids is an important feature of many mechanisms. In an automotive environment, proper delivery of liquids is essential for the functioning and maintenance of a motor vehicle. By way of example, a motor vehicle will not function without fuel, typically liquid gasoline. That same motor vehicle will not function properly without the proper amount of oil stored in the internal combustion engine allowing it to lubricate and cool itself. These are just two fluids in a particular environment that require close observation to make sure its host mechanism, i.e., the motor vehicle, can operate properly.
Currently, there are a number of ways in which a fluid level may be measured. The mechanisms used to measure the fluid level help determine if more fluid is required in order to continue the proper maintenance and operation of the host mechanism. Fluid level measuring mechanisms include floating arm mechanisms, pressure sensors, capacitive sensors, and ultrasonic sensors. The most commonly used fluid level measuring system is the floating arm mechanism.
The floating arm mechanism is an imperfect mechanism for several reasons. First, the floating arm mechanism requires moving parts inside a liquid-filled container. This requires increased time to install the floating arm mechanism and seal it and the container or reservoir. Resistive strips used by the floating arm mechanism are susceptible to contamination and can develop contact problems. The contamination and contact problems result in erroneous measurements.
A sensing assembly senses a level of a liquid in a reservoir. The sensing assembly includes a first input port for receiving a first input voltage signal. The sensing assembly also includes a second input port for receiving a second input voltage signal. An excitation circuit is electrically connected to the first and second input ports for receiving the first and second input voltage signals and for generating a first excitation signal and a second excitation signal. A receiving circuit is disposed adjacent the excitation circuit and defines a variable capacitance with the excitation circuit. The receiving circuit produces an output voltage variable with the level of liquid in the reservoir due to capacitance changes between the excitation circuit and the receiving circuit. The capacitance changes are due to dielectric changes created by the presence of the liquid.